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Old 26th September 2008, 12:40 AM   #1
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Question Need Help With Power Acoustik LT-980/2 Amp

Hey Everyone, Ryan here im new to the forum with hopes that this will become my new audio help HQ!

Well, lets get to the point shall we, I have an Power Acoustik LT-980/2 Amplifier. A pretty decent amp In My Own Oppinon, and cheap. Unfourtunately they stopped manufactoring this amp a couple years ago, and mine is not working. I bought this amp on Ebay and it supposedly worked when it was shipped out; or so the guy who sold me it says. After a few Emails and phone calls i got my money back, and he doesnt want the amp back, because well... who wants a broken amp!? So its my goal to Fix it! i have another in the mail soon so i cant complain too much but id really like to get it working.

I also have another quick question! How do you go about Chargeing a Capacitor Correctly? A Link to a Tutorial would be Great! Thanks!

So here are the symptoms.

~For the record, My Connections are Great, Grounded Twice, 20V Capacitor, 4 Gauge Wire From Cap, 4 Guage From Bat, and 2 6 Guage wires from Chasis. So that being said, and seeing as this is the only amp i own that wont work correctly in my vehicle... Its not my wireing, or Car.

1. I turn the amplifier on and it goes into Fault Protection mode and than flickers back to the power-on state for a split second then repeat!

2. I have opened the Amplifier and there are No burnt traces of Components that i can see. although i will say there is One Set of Mosfets and what looks like a smaller chip with a wavey sign below it on the bread board ( im guessing its a resistor of sorts?) that have a bit of a rust colored discoloration on them.

3. This particular board is used for not only one amp. Or so i "think" there are component spots that are missing components and solder, so this is why i mention this.

4. I can get power from a Fuse slot or the Power Connection to "I Think" every spot and component on the board. All of the previous is true, in the Exception that once again this board is used for many diffrent amplifiers and there is a 25 Amp fuse that only goes to One spot, and No Rail or components connect to it. I got creative and soldered two fuse pools together SLIGHTLY to see if this would rectify my problem, which it didnt.

5. When the amp is flickering between Power-On and Fault, it does make a slight power on Bump to the subwoofers assumeing i have any connected.


~ Finally. A Note. I emailed and called power acoustik, kissed a little butt and got ahold of the Components list and Schematics for the Board! Which as i write this i will look over more closely and examine my board.

Well i think thats it! Please Assist Me in this! Thanks Guys! Please, dont let me down!
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Old 26th September 2008, 01:58 AM   #2
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It probably has shorted output transistors.

The larger transistors (2SC4468 and 2SA1695?) are the outputs. If any read anything near 0 ohms between the legs of any indifvidual transistor, they are defective.
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Old 26th September 2008, 03:31 AM   #3
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please tell me you didnt just do those numbers off the top of your head..

PT# TR-2SA1694 / 2SA1694 TRANSISTOR
QTY. 4.000
LOC. Q112,Q114,Q212,Q214

PT# TR-2SC4467 / 2SC4467 TRANSISTOR
QTY. 4.000
LOC. Q111,Q113,Q211,Q213



Cause you were Realllllly Close.
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Old 26th September 2008, 03:31 AM   #4
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Default hmm..

I went ahead and tested all of the output transisters as well as the FETS, whats a Bad ohm rating? cause they all seem to be reading at the very least 10's. But i do have a question, the inner leg of the FETS all read 0 Ohms... Thats Normal Correct?
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Old 26th September 2008, 04:12 AM   #5
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I knew the smaller amp used the 4467/1694. I thought yours had more rail voltage and would use the ones I listed.

You read 0 ohms from what point to the center leg to get 0 ohms? If it was from the B+ terminal to the center leg, that's normal, otherwise, it's not.

You should have checked each individual transistor from legs 1-2, 1-3, 2-3. None should be near 0 ohms.
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Old 26th September 2008, 08:39 AM   #6
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Default wait a tic,

Ok, well its apparent that i am useing my ohmeter wrong... or something. I am connecting the Positive Lead one of the legs and the Negative/Ground to another... Should i be placeing one of the leads in the Ground or Battery Connectors for the Amp itself? because when i connect one of the leads to say 2-3 i get a Solid Ground.
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Old 26th September 2008, 08:39 AM   #7
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I firstly need to appologize for all the double posting im doing. unfourtunately im under the assumption that this forum does not posses the Edit Button. So that being said, let me go ahead and clearify a few things. I'm kinda learning as i go hehe. Well, I am connecting the Negative lead through the Battery+ and using the Positive Lead to test the Legs of the Trans. and FETS, I am almost positive the FETS are all good. The Trans. on the other hand have me a bit confused... Still connecting the Negative Lead through the Battery+ connector, and when i connect the Positive Lead to all three of the Legs of the Trans' i get readings around 10 Ohms. i am currently working on determining whats going on with the Ohm readings when i connect the Leads to the Trans. itself... When i connect the Positive to Any of the Middle Legs and use the negative lead on any outter leg i get a ground. Not suprised with that, if im not mistaken thats correct right? Now as i am testing here at my desk, i am finding that when i ground leg 2 and measure 1 i get a ground, on All of the Trans. and when i ground Leg 3 and test Legs 1 and 2 i get about half an ohm as a rating... This is all getting so confuseing as i am getting MANY diffrent readings now. So for now i shall stop and wait for an answer. Thank You Perry!

Also if the Schematic would help you to better assist me i can provide it to you.
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Old 26th September 2008, 09:07 AM   #8
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Touch and hold one meter lead to the center leg of a transistor. Then touch the other lead to first the left leg of the same transistor, notice the reading. Then take the lead off of the left leg and move it to the right leg of the same transistor, notice the reading. Check all 8 of the outputs in the manner stated above.
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Old 26th September 2008, 02:24 PM   #9
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The test procedure suggested above will work. If you want to understand more about the testing procedure, go to the 'Checking Bipolar Transistors' section of the basic repair page (link below).

http://www.bcae1.com/repairbasicsfor....htm#checkBJTs

Let us know what you find.

Yes, having the schematic would help.

babin_perry@yahoo.com
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Old 26th September 2008, 05:48 PM   #10
jol50 is offline jol50  United States
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I have three of those sitting here with blown outputs I need to buy. They are SK A1694 and C4467. Some audiobahn and kenwood use the 1694s too as well as others I'm sure.
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